Plant biomass contains considerable calorific value but most of it makes up robust cell walls, an unappetizing evolutionary advantage that helped grasses to survive foragers and prosper for more than 60 million years. The trouble is that this robustness still makes them less digestible in the rumen of cows and sheep and difficult to process in bioenergy refineries for ethanol fuel. Until now, with the discovery of a gene that controls that robustness.